RFD900x Best way to power with PPM passthrough

Hardware Multirotors
1

Hi All,
So I have been using the rfd900x radio with cube orange on my quadcopter for some time now. Earlier I directly connected the supplied cable along with the rfd bundle to the telemetry 1 port of the FC and the other end on the radio pins. It worked Ok. Later I wanted to remove the RC receiver from the rover and use the telemetry to control the craft so I hooked the receiver to the ground unit of the rfd900x modem with the ppm passthrough cable and same I did with the rover rfd900x. So this cable in effect connects the rover rfd to the RCIN of the cube and the base rfd to the receiver’s sbus port. Pictured below is the the cable.

d4rii_connection_with_ftdi
d4rii_connection_with_ftdi1080×810 199 KB
wo_case_to_pixhawk
wo_case_to_pixhawk1080×810 218 KB
rfd_900_cable
rfd_900_cable1080×844 78.2 KB

Now comes the dilemma that I am in. I have heard from many sources that one should not power the rfd radios directly from the pixhawk but from a separate BEC. My doubt is if my radio is getting the power from the telemetry 1 port of the cube as well as the RCIN rail of the cube then is safe for me to use no BEC or should I still go ahead and power it directly with a 5V BEC? If yes, would anyone kindly tell me the wiring diagram for it?
Please excuse if I sounded stupid somewhere.
Thanks in advance

2

I have powered an RFD900X from the telem1 port, BUT I had to turn the power down on the radio significantly. At 30db I was suffering signal loss that I attributed to power brown-outs. After turning the power level down to 22 or 24 db the problem went away and I still have over 3km of range. Suitable for that project.

In my other installation I have the used a separate BEC just for the radio. I do not connect the 5v leads on the RCIN or the telemetry so there is no chance of things getting mixed up. This works well and at full power there’s no issues.

3

Yeah the RCIN port is only designed to power a conventional RC receiver, it wont cope well with an RFD900

4

Absolutely never ever ever try to power the rfd900 from the rc in port. You risk blowing the internal reg and hence your flight controller

5

Update: Rewired the radios on all crafts.

Hi everyone, so I have rewired the RFD900x radios on all my quads to and external 5v power source.
Now my only doubt is, does the radio work well with 5v or does it need 5.3v as I read somewhere.
I only have 5v BECs available with my right now. For 5.3v I’ll have to get the variable once with an adjuster to set the desired voltage. Please give your inputs @Allister, @james_pattison and @xfacta.
Thanks

Cheers :smiley:

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6

5.0volts should be fine - the problem with running them from a flight controller is the ability to supply bursts of current without affecting the FC itself or other devices

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